In response to the requirements of both government and industry, means have been provided to avoid the passage of fumes to the atmosphere during the transfer of volatile fuels and liquids from a storage tank thereof, to a fuel tank or the like.
The system adapted to this purpose when applied to an automotive service station, is ordinarily referred to as a closed fuel system. In essence, the system comprises the basic means whereby to effect a fuel transfer operation. A manually operated nozzle is initially inserted into the fuel tank to be filled. Sealing means carried on the nozzle is positioned to form a vapor tight fit with the tank filler tube.
During the actual fuel transfer, fumes which evaporate from the fuel, as well as fumes and air which are displaced from the tank, are carried back through the nozzle. They are then returned to the fuel source or to an alternate accumulation point.
Seal tight nozzles of this type are found to be satisfactory in most instances for effecting the necessary transfer of fuel, as well as for automatically discontinuing fuel flow when the tank becomes filled. However, since the system is entirely segregated and sealed from the atmosphere, there is a chance for an undesired accumulation of vapors. This occurs when they are not properly conducted from the tank being filled.
To overcome the situation which might arise due to a closed system becoming overpressurized, means is usually provided in the fuel dispensing nozzle for discontinuing the flow in response to a predetermined increase in fuel tank pressure. It has been noted that in such systems however, because of the particular arrangement of the nozzle, and the facility therein for handling both liquid fuel and the vapor, under certain circumstances fuel which is pumped from the source, can be recycled through the nozzle. It would thereafter return to the source without ever entering the fuel tank being filled. This circumstance represents an untenable situation. Although the pumped volume of fuel is registered and charged to a customer, it nonetheless might not reach its destination.
The factors which lead toward recycling of the fuel are often prompted by some malfunction in the fuel pumping mechanism. This malfunction can originate at any of several elements within the system prior to fuel reaching the nozzle. In any instance, a characteristic of the malfunction is that the fuel pressure within the system, and within the nozzle itself, decreases noticeably.
Toward overcoming the problem of fuel recycling, there is presently disclosed a nozzle and means therein for automatically discontinuing fuel flow. This action is taken in response to a predetermined pressure decrease at the upstream side of the nozzle's main metering valve. The system comprises the necessary means for determining a pressure differential between a point within the nozzle's fuel flow passage, and the atmospheric pressure. These two reference points are utilized to stabilize the open, or flow condition of the main flow valve. When the stabilized pressure condition is upset due to decrease in pressure within the nozzle, a signal transmitted to the main flow jcontrol valve actuator automatically adjusts said main valve to shut down the fuel system.
It is therefore an object of the invention to provide a fuel dispensing nozzle capable of sensing a decrease in fuel flow volume, and of discontinuing flow through the nozzle. A further object is to provide a seal tight nozzle for a fuel system which is adapted to automatically adjust itself to discontinue fuel therethrough in response to a number of conditions within the system prompted either by overpressuring or underpressuring of the latter. A still further object is to provide a dispensing system for a volatile fuel in which a malfunction in the system, which would ordinarily prompt recycling of the fuel back to its source, is automatically stabilized by sensing of the condition within the dispensing nozzle.